Sometimes I start smoking and then decide to stop and leave it there to smoke the rest later. How long would I be able to leave it there without being lit and not affect the tobacoo, flavor if there's such a thing?
Many do it. It's called delayed gratification. Some will put down a pipe and finish it the next day. Sometimes after sitting overnight it's better. Long term, such as two or more days? I imagine at some point it's just going to dry out too much and become stale.
How long would you leave an open jar sitting around and still smoke the tobacco? Despite Forums preference for perfection in moisture content, fairly dry tobacco usually smokes well. Overnight, a few hours, a day, a few days ... usually not a problem, whether it's in an open bowl, in the pipe unsmoked, or in the pipe partially smoked, in my experience. Don't get too cavalier. A blend can dry out and be stale, harsh, burn too fast, or lose it flavor and nuance. Don't abuse the privilege, but generally, for short periods of time, it will be okay, in some cases slightly improved.